Eldo-XL: a software accelerator for the analysis of digital MOS circuits by an analog simulator

Eldo-XL is composed of a set of techniques developed on the basis of the Eldo analog simulator and integrated in it. Eldo-XL is targeted at the simulation of MOS digital circuits with minimal loss of accuracy compared to Eldo. The basis of Eldo-XL is a simpler MOS transistor model which allows the analytical solution of the nodal equations most of the time. The costly iterations associated the implicit solution are avoided and a large speed-up is obtained. The availability of a simpler relaxation algorithm can further enhance the performance on circuits with little feedback. All these acceleration techniques can be used on the digital part of a mixed analog/digital circuit without influencing the accuracy of the solution of the analog part. This paper presents the three techniques developed for Eldo-XL and attempts to show that a good efficiency can be reached without losing generality by combining a classical analog simulator with a dedicated evaluation engine for digital MOS circuits